Datasheet

LTC6994-1/LTC6994-2
19
699412fb
Power Supply Current
The Electrical Characteristics table specifies the supply
current while the part is idle (waiting for an input transi-
tion). I
S(IDLE)
varies with the programmed t
DELAY
and the
supply voltage, as described by the equations in Table 2,
valid for both the LTC6994-1 and LTC6994-2.
Table 2. Approximate Idle Supply Current Equations
CONDITION TYPICAL I
S(IDLE)
N
DIV
≤ 64
V
+
• N
DIV
• 7pF + 4pF
( )
t
DELAY
+
V
+
500kΩ
+ 2.2 •I
SET
+ 50µA
N
DIV
≥ 512
V
+
•N
DIV
• 7pF
t
DELAY
+
V
+
500kΩ
+ 1.8 •I
SET
+ 50µA
When an input transition starts the delay timing circuity,
the instantaneous supply current increases to I
S(ACTIVE)
.
I
S(ACTIVE)
= I
S(IDLE)
+ ∆I
S(ACTIVE)
applicaTions inForMaTion
∆I
S(ACTIVE)
can be estimated using the equations in Table 3,
assuming a periodic input with frequency f
IN
. The equa-
tions assume the input pulse width is greater than t
DELAY
;
otherwise, the output will not transition (and the increase
in supply current will be less).
Table 3. Active Increase in Supply Current
CONDITION DEVICE TYPICAL ∆I
S(ACTIVE)
*
N
DIV
≤ 64
LTC6994-1 f
IN
• V
+
• (N
DIV
• 5pF + 18pF + C
LOAD
)
LTC6994-2 f
IN
• V
+
• (N
DIV
• 10pF + 22pF + C
LOAD
)
N
DIV
≥ 512 Either Version f
IN
• V
+
• C
LOAD
*Ignoring resistive loads (assumes R
LOAD
= ∞)
Figures 14 and 15 show how the supply current increases
from I
S(IDLE
) as the input frequency increases. At higher
N
DIV
settings, the increase in active current is smaller.
f
IN
• t
DELAY
“IDLE”
POWER SUPPLY CURRENT (µA)
150
200
250
0.8
699412 F14
100
50
0
0.2
0.4
0.6
1.0
÷1, R
SET
= 50k
÷8, R
SET
= 50k
÷1, R
SET
= 100k
÷1, R
SET
= 800k
V
+
= 3.3V
INPUT PULSE WIDTH = 1.1 • t
DELAY
C
LOAD
= 5pF
R
LOAD
= ∞
f
IN
• t
DELAY
“IDLE”
POWER SUPPLY CURRENT (µA)
150
200
250
0.4
699412 F15
100
50
0
0.1
0.2
0.3
0.5
÷1, R
SET
= 50k
÷8, R
SET
= 50k
÷1, R
SET
= 100k
÷1, R
SET
= 800k
V
+
= 3.3V
f
IN
< 1/(2 • t
DELAY
) TO ALLOW RISING AND
FALLING DELAYS TO REACH THE OUTPUT
C
LOAD
= 5pF
R
LOAD
= ∞
Figure 14. I
S(ACTIVE)
vs Input Frequency, LTC6994-1 Figure 15. I
S(ACTIVE)
vs Input Frequency, LTC6994-2